The isoform type ofγsubunits of GABAA receptor is a molecular determinant of its pharmacological characteristics. At present, the existence of GABAA receptor in mammalian sperm is still a controversy. By using degenerate primers designed according to highly conserved region in all threeγ(γ1, γ2 andγ3) subunits cloned in rat brain, we performed reverse transcription polymerase chain reaction (RT-PCR) to examine the expression pattern of -γsubunits of GABAA receptor in rat testis. Only one 370 bp fragment was obtained from RT-PCR in rat testis and sequencing results showed that it representedγ1 subunit, but notγ2 orγ3 subunit. Using the cloned fragment as probe, a 3.8 kb transcript which in size as same asγ1 ubunit in rat brain was detected in rat testis mRNA by performing Northern blot assay. Furthermore, results of in situ hybridization assay confirmed thatγ1 subunit was expressed in round spermatids and spermatozoa, maybe also in secondary spermatocyte. These evidences proved that 71 subunit of GABAA receptor is exclusively expressed in rat testis and this feature may be the structural basis of the specific function of GABAA receptors in sperm acrosome reaction. The present isoform of gamma subunits of GABAA receptor is a molecular determinant of its pharmacological characteristics. At present, the existence of GABAA receptor in mammalian sperm is still a controversy. By using degenerate primers designed according to highly conserved regions in all three gamma (γ1, γ2 and γ3 ) subunits cloned in rat brain, we performed reverse transcription polymerase chain reaction (RT-PCR) to examine the expression pattern of-γsubunits of GABAA receptor in rat testis. Only one 370 bp fragment was obtained from RT-PCR in rat testis and sequencing results showed that it representedγ1 subunit, but notγ2 orγ3 subunit. Using the cloned fragment as probe, a 3.8 kb transcript which in size as same asγ1 ubunit in rat brain was detected in rat testis mRNA by performing Northern blot assay. situ hybridization assay confirmed thatγ1 subunit was expressed in round spermatids and spermatozoa, maybe also in secondary spermatocyte. These evidences prov ed that 71 subunit of GABAA receptor is exclusively expressed in rat testis and this feature may be the structural basis of the specific function of GABAA receptors in sperm acrosome reaction.